1. Field of the Invention
The present invention relates to a biochip reader and also to a method for correcting the influence of intensity distribution (shading) of a light source (excitation light).
Specifically, the influence of this shading is large in the scan-less type biochip reader in which a wide biochip range is measured simultaneously with a plurality of light beams.
2. Description of the Prior Art
This kind of scan-less type biochip reader is well known from the past (for example, refer to Patent Document 1). FIG. 1 is a configuration drawing indicating the essential part of an example of the scan-less type biochip reader described in Patent Document 1.
In FIG. 1, laser light (excitation light) emitted from a light source becomes parallel light and is incident to microlens array 1. Microlens array 1 is an arrangement of a plurality of microlenses (ML) and excitation light converged respectively by each microlens (ML) irradiates measurement sample 3 after transmitting dichroic mirror 2. Measurement sample 3 is constructed so that a plurality of cells (sites) is arranged in a two-dimensional manner and a sample is poured in each cell (site).
Fluorescent light from each sample is reflected by dichroic mirror 2 and is incident to lens 5 via barrier filter 4. Barrier filter 4 has the effect of acting to transmit fluorescent light from measurement sample 3 but to attenuate the excitation light reflected by measurement sample 3, and is used to eliminate the background light of a sample image. A sample image focused and formed by lens 5 is captured by camera 6.
According to such a configuration, a plurality of cells (sites) on a biochip can be measured at the same time with a scan-less method in which excitation light is not scanned.
[Patent Document 1]                Gazette for Japanese Laid-open Patent Application No. 2003-28799 (p. 6, FIG. 13)        
However, in such conventional biochip readers, the distribution of excitation light intensity becomes the distribution of excitation light intensity on the measurement plane of a biochip without change and thus excitation light intensity is different at each site even on the same chip.
Accordingly, conventional biochip readers have the following problems:    (1) There are portions on a biochip where excitation light is strong and portions on the same biochip where excitation light is weak. This affects the amount of fluorescent light emission. In particular, differences between these strong and weak light intensities are extremely large for scan-less type readers.    (2) If the quantities of light are simply corrected using a certain factor, they become unknown in the case where the absolute quantity of light calibration system using a power meter traceable to national standards is used.    (3) If the quantities of light are simply corrected using a certain factor, pixels may be easily saturated or the tones over the whole pixels of images may be lowered to the span.